JP2001054775A - Method and device for reducing lead and chlorine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the method and device for reducing both of lead and chlorine in a clinker. SOLUTION: In the method, a lead compd. is heated to a temp. above the boiling temp. of lead chloride under the presence of chlorine to convert the lead compd. to the lead chloride and to evaporate and remove the lead chloride. In this case, the lead compd. is evaporated and removed by adjusting chlorine quantity in excessive quantity than chemical equivalence based on lead content, moreover, residual chlorine is removed by converting the chlorine to alkali chloride by introducing alkali.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for removing lead and a lead compound (both of which are referred to as a lead compound) by utilizing chlorine, the effect of removing the lead compound is high, and the residual chlorine amount is small. It relates to a method for reducing lead and chlorine. This method can be widely applied to the case where lead and chlorine are removed from waste and reused. In particular, it is useful in the technical field of using incinerated ash of domestic and industrial waste as a cement raw material.

[0002]

2. Description of the Related Art As a means for removing lead compounds contained in wastes, there has been conventionally known a method of baking in the presence of chlorine to convert the lead compounds into lead chloride and volatilize them. At this time, if an alkali metal is present together with the lead compound, the alkali metal is more easily bonded to chlorine than lead, so that the lead compound is affected by the alkali metal, part of which is converted to lead oxide and the volatilization of lead is suppressed. , Lead content increases.
If the amount of chlorine is increased to solve this problem, the residual amount of the lead compound is reduced, but there is a problem that the residual amount of chlorine is increased this time. There is also a method of evaporating the lead oxide in the clinker by raising the firing temperature. However, it is necessary to heat the firing temperature to 1350 ° C. to 1400 ° C. or higher at which the lead oxide evaporates, and the clinker softens and the It is not preferable because it adheres to the brick wall surface and the amount of heat increases.

[0003]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems in a method for removing lead using chlorine, and it is an object of the present invention to adjust the amount of chlorine relative to a lead compound and the timing of introducing alkali. As a result, the chlorine content in the clinker is reduced to 1000 ppm or less, preferably several tens of ppm, and the lead content in the clinker is reduced to environmental standards within a range in which the alkali content in the clinker does not exceed 0.75 wt%. It is intended to provide a method for reducing the content to 60 ppm or less.

[0004]

That is, the present invention provides a method of heating a material containing a lead compound to a temperature higher than the boiling point of lead chloride in the presence of chlorine, converting the lead compound into lead chloride, and volatilizing and removing the amount of chlorine. Lead / chlorine characterized by adjusting the amount to be more than the chemical equivalent to the lead content to volatilize and remove the lead compound, further introducing an alkali to convert the remaining chlorine into an alkali chloride and removing by heating. To a method for reducing the amount of odor.

In the above method, preferably, the amount of chlorine is adjusted to an excess of a chemical equivalent to the total amount of the lead compound and the alkali to volatilize and remove the lead compound, and further, an alkali is introduced to remove the remaining chlorine.・ This is a method for reducing chlorine.

In the above methods (1) and (2) for reducing lead and chlorine, specifically, the amount of chlorine is adjusted according to the following formula (II). The amount of alkali added is adjusted according to the following formula (III). 1 <([Cl]-[R]) / [Pb] <15 (II) ([Pb] is the chemical equivalent of the lead compound content, [R] is the chemical equivalent of the alkali metal compound content, [Cl] Is the chemical equivalent of chlorine. 1 <([R] + [R1]) / [Cl] <3 (III) ([R] and [Cl] are the same as above, [R1] is the alkali metal compound to be added. Chemical equivalent, and ([R] + [R1]) is the amount of R ₂ O in clinker that is 0.75 wt% or less)

Further, the present invention provides a method of producing a cement clinker by calcining a cement raw material in a kiln to adjust the amount of chlorine in the raw material to an excess of a chemical equivalent to the lead content and calcinate the lead compound. The present invention relates to a method for reducing lead and chlorine, which volatilizes and removes and further introduces an alkali from the clinker discharge side of the kiln or from the middle of the kiln to convert chlorine remaining in the clinker into an alkali chloride and remove it.

[0008] Lead in the production of the above cement clinker
In a rotary kiln for producing clinker, the length (L) with respect to the diameter (D) of the kiln is in the range of 4D to 12D from the discharge end, and 50% by weight or more of the total alkali mixed into the raw material in the kiln. Including a method to introduce.

Further, the present invention relates to a method for reducing lead and chlorine in the production of cement clinker, wherein a means for introducing an alkali material is provided at a clinker discharge end or a central portion of the rotary kiln. A reduction device is provided.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The lead / chlorine reduction method of the present invention will be described below in detail based on embodiments. The method of the present invention is a method of heating a material containing a lead compound to a temperature higher than the boiling point of lead chloride in the presence of chlorine, and converting the lead compound to lead chloride to volatilize and remove the amount of chlorine relative to the lead content. This is a method for reducing lead / chlorine, which comprises adjusting the amount to an excessive amount, volatilizing and removing a lead compound, and then introducing an alkali to convert residual chlorine into an alkali chloride and removing it by heating.

In the present invention, the amount of chlorine is adjusted so as to be slightly larger than the chemical equivalent of the lead content of the raw material. Specifically, for example, the chemical equivalent of chlorine is [C
l], assuming that the chemical equivalent of lead is [Pb], the chlorine content of the reaction system is adjusted to the range of the following formula (I) with respect to the lead content. 1 <[Cl] / [Pb] <15 ... (I)

When the raw material contains an alkali metal compound together with a lead compound, the amount of chlorine is adjusted to be a little excessive with respect to the chemical equivalent to the total amount of these. That is, when the chemical equivalent of the alkali metal content is [R], the chlorine content is adjusted to the range of the following formula (II) with respect to the lead content and the alkali content. 1 <([Cl] − [R]) / [Pb] <15... (II)

In the above formulas (I) and (II), if the chlorine content is smaller than 1, the chlorine content of the lead compound or the alkali metal compound becomes insufficient, and the residual amounts of the lead compound and the alkali metal increase. On the other hand, when the chlorine amount exceeds 15, the residual amount of chlorine is large, and a large amount of alkali is required in the next step to remove the chlorine. As shown in Examples described later, the chlorine amount is determined by the above formulas (I) and (II).
Two or more and ten or less are preferable.

When the method of the present invention is applied to the production of cement clinker, the amount of chlorine in the chlorination reaction system is determined based on the amounts of chlorine and alkali metals contained in the raw material of cement clinker as described in (I) and (II) above. Adjust so that it is within the range of the formula. Specifically, when the amount of chlorine is smaller than the amount of lead compound or alkali in the raw material, a chlorine source such as calcium chloride is supplemented. On the other hand, when the amount of chlorine is significantly larger than the range of the above formulas (I) and (II) with respect to the amount of the lead compound and the alkali, an alkali source such as sodium carbonate is added.

Next, at the stage where the chlorination of the lead compound and the volatilization of the generated lead chloride have progressed, an alkali (an alkali metal source such as sodium carbonate) is introduced into the reaction system, and chlorine remaining in the clinker is removed by sodium chloride. Turned into alkali chlorides and removed. At this time, if the timing of introducing the alkali is too early, it is not preferable because chlorination of the lead compound is hindered.

The amount of the alkali (alkali metal source) to be introduced may be determined as follows. That is, the amount of chlorine remaining in the clinker is calculated from the amount of chlorine adjusted according to the above formulas (I) and (II), and the amount of alkali added is determined within the range of the following formula (III) with respect to this amount of chlorine. 1 <([R] + [R1]) / [Cl] <3 (III) Here, [R] and [Cl] are the same as above, and [R1] is the chemical equivalent of the alkali compound to be added. . Further, in ordinary cement, the alkali content (R ₂ O) is controlled to 0.75 wt% or less, so that in the above formula (III), the total amount of alkali ([R] + [R1]) is 0.75wt of R ₂ O in clinker
%.

When the amount of alkali in the above formula (III) is blown by air or the like, it is preferable to consider the scattering rate of gas discharged outside the system. The scattering rate of the alkali discharged out of the system can be calculated by analyzing the amount of alkali in dust and clinker against the amount of alkali added.
Ratio of alkali increase [R2] in dust to [R1],
ie It is obtained based on [R2] / [R1] × 100. Also,
During operation, the produced clinker is analyzed by fluorescent X-ray,
[R], [R1], [Cl], and [Pb] are obtained, and the results are fed back to the next clinker production to adjust the chlorine amount and the alkali addition amount.

In the production of cement clinker using a rotary kiln, the timing of alkali introduction in the above reaction system can be adjusted depending on the alkali introduction position of the kiln. Specifically, the length (L) is set within a range of 4D to 12D from the clinker discharge end with respect to the diameter (D) of the kiln, and 50 wt% of the total alkali mixed into the raw material in the kiln.
It is preferable to introduce the above. In the range where the length (L) is larger than 12D (ie, the range near the entrance of the kiln), the chlorination reaction is in the initial stage, and the lead compound is not sufficiently volatilized. When an alkali is introduced into this range, chlorine is consumed by the alkali, so that chlorination of the lead compound is suppressed and the residual amount of lead increases. On the other hand, if the length (L) of the alkali introduction position is smaller than 4D, it is close to the exit of the kiln, and the reaction time of the introduced alkali is insufficient.

In order to introduce alkali into the above-mentioned range of the kiln, it is preferable to provide a means for introducing alkali at the clinker discharge end (outlet) of the kiln. Preferably, at the kiln entrance,
Raw material charging means, chlorine source charging means, and alkali source charging means are provided so that the chlor-alkali balance of the raw material can be adjusted.Furthermore, at the discharge end (outlet) of the kiln, an alkali charging means for removing residual chlorine is provided. Provide. As the charging means, for example, a configuration may be employed in which a pipeline for transporting the alkali by air is provided, and a blowing nozzle is provided at the tip in the kiln. By adjusting the blowing speed, alkali can be introduced into the above-mentioned range of the kiln. An opening / closing lid is provided in the middle of the kiln,
A method in which the alkali is added from the middle of the kiln by means such as opening the lid mechanically every rotation and introducing the alkali may be used.

FIG. 1 shows an example of a preferred apparatus configuration according to the present invention. The apparatus shown in FIG. 1 is an apparatus in which the present invention is applied to a clinker manufacturing apparatus for cement, and a hopper 1 for supplying a raw material, a chlorine source and an alkali source to an inlet side of a rotary kiln 6.
3, 14, and 15 are provided, and these are connected to an inlet of the kiln 6 via a conveyor 7. Also,
An exhaust gas cooling duct 8 is connected to the kiln inlet, and a cyclone 9 is interposed therebetween. The volatilized salts in the exhaust gas are led to a cyclone 9 via a cooling duct 8 to be separated and concentrated, and a part thereof is sent to a kiln. A bag filter 10 is connected to the cyclone 9, and dust such as lead collected here is sent to a refining process and collected. The exhaust gas is discharged outside the system via the blower 11. On the other hand, at the outlet of the kiln 6, an alkali injection means 1 is provided together with a burner 4 and a cooler 5 for cooling the recovered clinker. The charging means 1 has a blower 2 and a pipe for conveying the alkali by air, and a nozzle 3 provided at the tip of the pipe in the furnace.
An alkali source is blown into the furnace from the nozzle 3 at a flow rate of m / s.

[0021]

According to the present invention, the residual amount of chlorine as well as the residual amount of lead can be greatly reduced. In particular,
As long as the alkali content in the clinker does not exceed 0.75 wt%, the chlorine content in the clinker can be reduced to 1000 ppm or less, preferably several tens ppm. Further, the lead content in the clinker can be reduced to a level of 60 ppm or less, which meets environmental standards. As described above, according to the present invention, the lead content and the chlorine content in the waste can be effectively reduced, and particularly, the harmful lead content can be reduced, so that the safety is enhanced, and the waste disposal can be performed safely. Can be done.
It is also useful for recovering lead. Furthermore, the treatment of municipal refuse incineration ash and sewage sludge incineration ash according to the present invention can significantly reduce the residual amounts of lead and chlorine that are undesirable for cement, which is advantageous when reusing these as cement raw materials.

[0022]

EXAMPLES The present invention will be specifically described below with reference to examples.

Example 1 Raw materials for cement preparation (Na ₂ O: 1.4 wt%, K ₂ O: 0.8 wt%, Cl: 2.
7 wt%, Pb: 1800 ppm, igloss: 33 wt%) 1500 kg / h, 7 kg / h of calcium chloride was added, and the mixture was charged into a rotary kiln shown in FIG. h was manufactured. The amount of chlorine, alkali and lead in the clinker is shown in No. 1 of Table 1. On the other hand, the results obtained by adding sodium carbonate to the above-mentioned raw material 1500 kg / h and adding 1 kg / h, 4 kg / h, and 6 kg / h respectively and calcining are shown in Table 1.
No. 2 to No. 4 are shown.

In the results of No. 1 to No. 3, the lead content of the clinker was reduced to 22 ppm due to the presence of a sufficient amount of chlorine. However, the residual chlorine is slightly high at 0.23 to 0.94 wt%, and almost no alkali remains, and the residual chlorine evaporates as alkali chloride. The alkali chloride is collected by the bag filter 10 as dust. On the other hand, as shown in No. 4, the amount of chlorine minus the amount consumed by alkali
When ([Cl]-[R]) becomes 1.5 equivalents to the lead content, the lead content remaining in the clinker becomes slightly higher. If the amount of chlorine relative to the lead content is less than 1 equivalent, lead will remain even if the entire amount of chlorine reacts. Therefore, the amount of chlorine {([Cl]-[R]) / [Pb]} relative to the lead content needs to be more than 1 equivalent, preferably 2 equivalents or more. Thereby, the lead content in the clinker can be reduced to several tens ppm.

Next, an example (No. 5 to No. 7) in which the amount of chlorine in the raw material system before the calcination was adjusted to the above range was charged into a rotary kiln, and an alkali (sodium carbonate) was added during the calcination. Looking at the example of No. 5, the chlorine content of the clinker is slightly high at 0.16 wt% even when 50 kg / h of sodium carbonate is added since the chlorine content with respect to the lead content exceeds 15 equivalents. On the other hand, in the examples of No. 6 and No. 7, the amount of chlorine relative to the lead content was in the range of 2 to 10 equivalents, and 25 kg of sodium carbonate was added thereto.
/ h, 10kg / h (in the range of ie.1 <{([R] + [R1]) / [Cl] <3)
By the addition, the amounts of lead, chlorine and alkali in the clinker are all greatly reduced. from this result,
The amount of chlorine relative to the lead content is suitably less than 15 equivalents,
2-10 equivalents are preferred. Further, the amount of alkali ([R] + [R1]) / [Cl]) added at the time of firing is preferably an amount exceeding 1 equivalent to less than 3 equivalents.

[0026]

[Table 1]

Example 2 With respect to the sample No. 1 of Example 1, the respective residual ratios of the lead, alkali and chlorine contained in the clinker to the raw materials were examined for each firing range in the kiln. The result is shown in FIG. The firing range was indicated by the length (L) from the burner side (outlet side) with respect to the kiln diameter (D). This example is a non-treated calcination state in which component adjustment of raw materials and alkali addition at the time of calcination are not performed, but as shown in the drawing, the inside of the kiln has a range of L / D = 12 or more (range on the inlet side). Since it is the initial stage of chlorination, the lead content and the alkali content are high together with the chlorine content, but the chlorination and the volatilization of the chloride proceed as the outlet side is reached, and the lead content and the alkali content increase with the chlorine content. The amount decreases, and L / D = 12
In the range of ４4, chlorine still remains considerably, but lead and alkali are greatly reduced. When L / D = 4 or less, the lead content becomes almost zero, and the alkali content is reduced to a level of 40 wt% or less. It becomes almost constant. Therefore, L / D =
By adding an alkali in the range of 12 to 4, the reaction with residual chlorine is promoted to generate an alkali chloride, whereby the amount of residual chlorine can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a kiln provided with a lead / chlorine reducing unit according to the present invention.

FIG. 2 is a graph showing the residual ratio of chlorine, lead and alkali in a kiln.

Continued on the front page (72) Inventor Norihisa Tanaka 2-4-2 Daisaku, Sakura City, Chiba Pref. Inside the Sakura Research Laboratories, Pacific Cement Co., Ltd. (72) Inventor Koichiro Sato 2-4-2 Daisaku, Sakura City, Chiba Pref. Pacific Cement Stock 4D004 AA36 AB03 AB06 BA02 BA05 CA30 CA34 CB09 CC11 CC12 DA02 DA03 DA06 DA10

Claims (7)

[Claims] 1. A method of heating a material containing a lead compound to a temperature higher than the boiling point of lead chloride in the presence of chlorine to convert the lead compound into lead chloride and volatilize and remove the chlorine content relative to the lead content. A method for reducing lead and chlorine, comprising adjusting a chemical equivalent to an excess amount to volatilize and remove a lead compound, further introducing an alkali to convert residual chlorine into an alkali chloride, and removing by heating. 2. The method according to claim 1, wherein the amount of chlorine is adjusted to an excess of a chemical equivalent to the total amount of the lead compound and the alkali to volatilize and remove the lead compound, and further introduce an alkali to remove residual chlorine. How to reduce lead and chlorine. 3. The method of claim 2, wherein the amount of chlorine is
Lead and chlorine reduction method adjusted according to (II). 1 <([Cl]-[R]) / [Pb] <15 (II) ([Pb] is the chemical equivalent of the lead compound content, [R] is the chemical equivalent of the alkali metal compound content, [Cl] Is the chemical equivalent of chlorine) 4. The method of claim 1, 2 or 3,
A method for reducing lead and chlorine in which the amount of alkali added is adjusted according to the following formula (III). 1 <([R] + [R1]) / [Cl] <3 (III) ([R] and [Cl] are the same as above, [R1] is the chemical equivalent of the alkali metal compound to be added, and ([ [R] + [R1]) is an amount such that R ₂ O in the clinker becomes 0.75 wt% or less.) 5. When producing a cement clinker by calcining a cement raw material in a kiln, the amount of chlorine in the raw material is adjusted to an excess of a chemical equivalent to the lead content and calcined to volatilize and remove the lead compound. The method for reducing lead and chlorine according to any one of claims 1 to 4, wherein an alkali is introduced from the clinker discharge side of the kiln or from the middle of the kiln to remove chlorine remaining in the clinker into alkali chloride. 6. A rotary kiln for producing a clinker, wherein the length (L) with respect to the diameter (D) of the kiln is in the range of 4D to 12D from the discharge end, and 50% by weight or more of the total alkali mixed into the raw material in the kiln. The method for reducing lead and chlorine according to claim 5, which is introduced. 7. An apparatus for reducing lead and chlorine, comprising means for introducing an alkaline material at a clinker discharge end or a central portion of a rotary kiln.